1. Field of the Invention
The present invention relates to a color cathode ray tube apparatus having an in-line type electron gun assembly and, more particularly, to an in-line type color cathode ray tube apparatus having a deflection unit.
2. Description of the Related Art
In an in-line type color cathode ray tube apparatus, an envelope is constituted by a panel, a neck, and a funnel connected between the panel and neck. A phosphor screen is formed on an inner surface of the panel upon deposition of phosphor stripe layers for emitting red, green, and blue light rays. An electron gun assembly for emitting three electron beams toward this phosphor screen is arranged in the neck. A deflection magnetic field generator is mounted on an outer surface of the funnel to horizontally and vertically deflect electron beams emitted from the electron gun assembly so that the phosphor screen is properly scanned by the electron beams. In addition, a shadow mask is arranged near the phosphor screen so as to oppose the inner surface of the panel. A large number of apertures are formed in the shadow mask in a predetermined arrangement such that electron beams passing through the apertures are accurately landed on three phosphor strips.
In order to cause three electron beams generated from the electron gun assembly to be accurately converged on a convergent point near the phosphor screen and accurately landed on three corresponding phosphor strips or dots, the deflection unit produces a pincushion-shaped horizontal deflection magnetic field and a barrel-shaped vertical deflection magnetic field inside the funnel. That is, the deflection unit produces a self-convergence type magnetic field.
A cathode ray tube using such a self-convergence type magnetic field as a deflection magnetic field has many advantages, e.g., various terminals for convergence adjustment or a convergence circuit can be omitted. However, in the cathode ray tube using the self-convergence type magnetic field, since distortion of a magnetic field is utilized for convergence, the shape of electron beams is distorted on the phosphor screen, thereby degrading the resolution in a color picture tube. More specifically, as shown in FIG. 1A, in an end portion area on the phosphor screen along its horizontal axis, an electron beam spot is separated into horizontally elongated bright core portion 1 and vertically elongated dark halo portion 2 to be formed into a distorted shape. In an end portion area on the phosphor screen along its vertical axis, the electron beam spot is separated into vertically elongated small bright core portion 3 and vertically elongated large dark halo portion 4 to be formed into distorted shape.